3:

a:Các tia trên hình là Ax,Ay,Bx,By,Cx,Cy

=>Có 6 tia

b: AB<AC

=>B nằm giữa A và C

=>AB+BC=AC

=>BC=4cm

c: AI=3/2=1,5cm

CI=7-1,5=5,5cm

 C NHA BN CÂU 45 KO LÀM ĐC

Bài 3:

Số học sinh kém là:

40-8-10-20=2(bạn)

Tỉ số phần trăm giữa số học sinh giỏi so với lớp là:

8:40=20%

Tỉ số phần trăm giữa số học sinh khá so với lớp là:

20:40=50%

Tỉ số phần trăm giữa số học sinh trung bình so với lớp là:

10:40=25%

Tỉ số phần trăm giữa số học sinh yếu so với lớp là:

2:40=5%

Câu 2.

\(C=\dfrac{N}{20}=\dfrac{4080}{20}=204\)(chu kì)

\(L=\dfrac{N}{2}\cdot3,4=\dfrac{4080}{2}\cdot3,4=6936A^o\)

\(G=X=30\%\cdot4080=1224nu\)

\(A=T=\dfrac{4080-2\cdot1224}{2}=816nu\)

\(a.C=\dfrac{N}{20}=204\)

\(b.L=\dfrac{Nx3,4}{2}=6936A\)

\(c.A=T=20\%N=816;G=X=30\%N=1224\)

\(d.rN=\dfrac{N}{2}=2040\)

b.L=Nx3,4/2=6936A

8D 5D 6B

MN là đường trung bình tam giác SAB \(\Rightarrow\) MN song song và bằng 1 nửa AB

Gọi P là trung điểm AD \(\Rightarrow PQ||AB\Rightarrow PQ||MN\Rightarrow P\in\left(MNQ\right)\)

\(\Rightarrow\) MNQP là thiết diện của chóp và (MNQ)

Do MN song song PQ \(\Rightarrow\) MNQP là hình thang

Lại có M, P là trung điểm SA, AD \(\Rightarrow MP=\dfrac{1}{2}SD\)

Tương tự \(NQ=\dfrac{1}{2}SC\Rightarrow MP=NQ=\dfrac{b\sqrt{3}}{2}\)

\(\Rightarrow\) Thiết diện là hình thang cân

\(PQ=AB=a\) ; \(MN=\dfrac{1}{2}PQ=\dfrac{a}{2}\)

Kẻ \(MH\perp PQ\Rightarrow PH=\dfrac{PQ-MN}{2}=\dfrac{a}{4}\)

\(\Rightarrow MH=\sqrt{MP^2-PH^2}=\sqrt{\dfrac{3b^2}{4}-\dfrac{a^2}{16}}\)

\(S=\dfrac{1}{2}\left(MN+PQ\right).MH=\dfrac{3a}{4}.\sqrt{\dfrac{3b^2}{4}-\dfrac{a^2}{16}}\)

dạ cảm ơn thầy ạ

=55,19/24+24+19,22

=2,2+24+19,22

=26,2+19,22

=45,42

sai đề rồi bạn nhé

\(\left(138,4-83,21\right):24+24+19,22\)

\(=\left(\frac{692}{5}-\frac{8321}{100}\right):24+\left(24+\frac{961}{50}\right)\)

\(=\left(\frac{13900}{100}-\frac{8321}{100}\right):24+\left(\frac{1200}{50}+\frac{961}{50}\right)\)

\(=\frac{5579}{100}:24+\frac{1891}{50}\)

\(=\frac{5579}{2400}+\frac{90768}{2400}\)

\(=\frac{96347}{2400}\)

1.Ha Noi is Bigger than Ho Chi Minh City.

2.He is more intelligent than his brother.

3.My house is older than her house.

4. This book is more expensive than that one.

5.Dogs are more clever than cats.

6.The boys are taller than the girls.

7.She is better at Engish than me.

8.My morther is busier than my father.

9. Hue is farther than Nghe An.

10.I am shorter than my sister.

11.These students are more intelligent than those.

12.The pen is cheaper than the book.

13.Ho Chi Minh City is more crowded than Hung Yen.

14.This girl is more pretty than those.

15.Her new car is more beautiful than her old one.

16.This tree is greener than that tree.

17.I am taller than my morther.

18. The rabbit is quickly than the tortoise.

18.Canada is larger than the USA

1.Ha Noi is Bigger than Ho Chi Minh City.

2.He is more intelligent than his brother.

3.My house is older than her house.

4. This book is more expensive than that one.

5.Dogs are more clever than cats.

6.The boys are taller than the girls.

7.She is better at Engish than me.

8.My morther is busier than my father.

9. Hue is farther than Nghe An.

10.I am shorter than my sister.

11.These students are more intelligent than those.

12.The pen is cheaper than the book.

13.Ho Chi Minh City is more crowded than Hung Yen.

14.This girl is more pretty than those.

15.Her new car is more beautiful than her old one.

16.This tree is greener than that tree.

17.I am taller than my morther.

18. The rabbit is quickly than the tortoise.

18.Canada is larger than the USA

1. thinner

2.bigger

3.the happiest

4. the best

5.dirtier

6. longest

7. older

8.lower,the shortest

9. larger

10. the most